Neural bases of focusing attention in working memory: an fMRI study based on group differences.

Using fMRI, we investigated neural substrates for focusing attention in working memory. To explore this focusing effect, two kinds of reading span test (RST), focused and nonfocused, were performed. In the focused RST (F-RST), the target word to be maintained was the focus word in the sentence. In the nonfocused RST (NF-RST), the target word was not the focus word in the sentence. In both RST conditions, significant activations were found in three main regions: left dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC), and left superior parietal lobule (SPL). In addition, fMRI signal changes increased in the left SPL in the NF-RST condition. These findings suggest that the neural substrates of focusing attention are based on SPL and ACC-DLPFC networks. Furthermore, there were group differences in the focusing effect between high-span and low-span subjects: High-span subjects showed focusing effects (supported by SPL control) greater than those of low-span subjects.